Method for producing naphthenes



United States Patent IVIETHOD FOR PRODUCING NAPHTHENES George D. Kittredge, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed July 29, 1957, Ser. No. 674,596

11 Claims. (Cl. 204-162) This invention relates to a method for producing naphthenes. In one aspect, the invention relates to a. method for converting paraflins to naphthenes by exposing the paraffin; to high energy gamma radiation. In a particular aspect, the invention relates to a method for converting gasoline boiling range parafllns to naphthenes under the influence of gamma radiation.

During the past several years, the octane requirements of internal combustion engines for passenger automobiles has constantly increased, placing an ever increasing burden upon refiners to develop ways of upgrading low octane fuels to higher octane values. One of the major fields of activity has been the development of better methods of conversion of parafiins to naphthenes, since the naphthenes have a much higher octane value than the paraflins.

It is, therefore, an object of this invention to provide a method for conversion of paraifins to naphthenes. It is another object of the invention to provide processes for improving the antiknock quality of gasoline boiling range paratfins.

Thus, according to the invention, there is provided a process for converting paraflins to naphthenes which comprises irradiation of the paraflins with gamma rays. The process is usually applied to paraffins boiling not over 600 F., although higher boiling paraffins are applicable. The process is especially advantageous as applied to gasoline boiling range paraflins, that is, C, paraflins to paraffins boiling up to 400 F. Particularly useful for preparing high octane blending stocks are the paraffins containing 5 to carbon atoms. As feedstocks, the normal paraifins are especially useful since the greatest increase in octane number is obtained starting with the normal parafins.

An especially advantageous process comprises irradiating gasoline boiling range paraflins and thereby obtaining a reaction product increased in naphthene content, and thereafter subjecting said product of irradiation to a reforming operation to reform the naphthenes to the even higher octane aromatics. In such a process, the feed can contain both normal and isoparaffins, but it is especially advantageous to separate the isoparaffins from the normal paraffins before the irradiation, the isoparafiins already having a quite high antiknock value. The product from the reforming operation can then be blended back with the separated isoparaifins to produce a very high octane blending fuel.

In accordance with the procms of the invention, the total dosage of irradiation of gamma rays to which the paraflins are exposed is in the range of 1x10 to 1x10 rep. (Roentgen equivalent physical). The rate of exposure to the gamma radiation is generally at the rate of 10 to 10 rep. per hour, preferably 10 to 10 rep. per hour, although higher or lower rates can be employed.

A wide range of temperatures during the reaction can be employed without any great effect upon the course of the reaction, and temperatures can range from 0 F.

2,956,942 Patented Oct. 18, 1960 or lower to as high as the thermal cracking temperature of the paraflin being irradiated. Usually temperatures below 300F. are employed.

Numerous sources of gamma rays for irradiation of the hydrocarbons are available. Such sources as spent fuel elements from nuclear reactors are quite satisfactory and may be very economically used, for these are ordinarily allowed only to deteriorate in activity and then reprocessed for recovery of the fissionable material. By using these spent fuel elements in this process, the radiant energy available as gamma rays is put to use in beneficiating gasoline boiling range hydrocarbons. Other sources of gamma rays, of course, may be utilized, for example, radioactive materials such as cobalt-60 and similar radioactive materials. Any other suitable source of gamma radiation can be used.

The irradiation can, of course, be carried out in either batch or continuous manner, continuous processes ordinarily being preferred because of greater convenience of operation. In either mode of operation, the irradiation is preferably carried out in the absence of oxygen, for

the presence of oxygen during irradiation can cause an increase in existent gum. Obviously, such an increase in the gum content of hydrocarbons to be used as motor fuels is undesirable.

The irradiation of parafi'ins converts at least a portion of the paraflins to naphthenes, and these naphthenes are highly useful a blending materials for spark-ignited internal combustion engines. The upgrading is most effective when the straight chain parafiins are converted to naphthenes, for the greatest increase in octane number is accomplished by this conversion. Obviously, either straight run gasoline or natural gasoline may be used as a source of the paraflins, and it is usually desirable that the straight chain paraflins be first separated from the remainder and the straight chain paraflins then be subjected to irradiation. The irradiated hydrocarbons can then be fractionated to separate the naphthenes and the unconverted parafiins recycled to the irradiation step. The naphthenes so produced can then be blended with the isoparafiins separated from the original gasoline to produce a high performance fuel.

Example I Separate samples of technical grade normal pentane and technical grade normal hexane were subjected to gamma irradiation from spent fuel elements from the nuclear reactor known as the Materials Testing Reactor, operated for the Atomic Energy Commission, National Reactor Testing Station, Idaho. The samples were irradiated in sealed containers at ambient temperature (about F.). The radiation dosages were about l 10 rep., employing an average rate of exposure of about 7.5 X 10 and 6.1 X 10 rep. per hour for the hexane and the pentane, respectively. Analysis of the charged hydrocarbons and irradiated hydrocarbons are shown in the table:

It is evident from these data that the parafiins were converted to naphthenes in a very substantial amount and with quite high efi'iciency.

3 Example 11 Several heavy distillate fractions were irradiated as set forth with respect to the irradiation of normal pentane and normal hexane in Example I. In the following table, the compositions of each of three samples are shown both before and after irradiation, the right-hand column in each case being the composition after irradiation.

1 From catalytic cracking.

All three samples received a total dosage of about 1x10 rep. and at an average rate of 7.7)(10 rep./hr., 7.1 X 10 rep/hr. and 6.1)(10 rep./hr. for the alkylate, kerosene and cycle oil samples, respectively.

As will be evident to those skilled in the art, various modifications of this invention can be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit or scope of the dis closure or from the scope of the claims.

I claim:

1. A process of producing naphthenes which comprises exposing a parafiin to a total dosage of gamma radiation of 1x10 to l 10 rep. units in the absence of metallic vapors, and thereby forming naphthenes, wherein the said paraffin is a gasoline boiling range paratfin from C parafiins to those boiling up to 400 F.

2. A process of producing naphthenes which comprises exposing a parafiin to a total dosage of gamma radiation of 1X10 to 1x10 rep. units in the absence of metallic vapors, and thereby forming naphthenes, wherein the said parafiin contains 5 to carbon atoms per molecule.

3. A process of claim 1 wherein said paraflin is a normal paraflin.

4. A process of claim 1 wherein said parafiin is an isoparaffin.

5. A process for producing naphthenes from paralfins which comprises exposing said paraffins to a total dosage of gamma radiation of 1x10 to 1x10 rep. units in the absence of metallic vapors, at a rate of exposure from 1x10 to l 10 rep. per hour, and thereby forming naphthenes, the said parafiins being exposed to gamma radiation being gasoline boiling range parafiins from C paraifins to those boiling up to 400 F.

6. A process for producing naphthenes from parafiins which comprises exposing said paraflins to a total dosage of gamma radiation of 1X10 to 1x10 rep. units in the absence of metallic vapors, at a rate of exposure from l l0 to 1x10 rep. per hour, and thereby forming naphthenes, the said parafiins being exposed to gamma radiation being gasoline boiling range paraffins from C parafiins to those boiling up to 400 F.

7. Producing naphthenes by exposing a paraflin to gamma radiation and thereby forming said naphthenes, the said parafiins being exposed to gamma radiation being gasoline boiling range parafiins from C paraflins to those boiling up to 400 F 8. A process of claim 1 wherein the temperature during said exposure is maintained within the range from zero to 300 F.

9. A process which comprises separating isoparaflins and normal paraifins from a gasoline; exposing the normal parafi'ins to a total dosage of gamma radiation of 1x10 to 1X 10 rep. units in the absence of metallic vapors, thereby forming naphthenes; reforming said naphthenes to aromatics, and combining said aromatics with said isoparatfins to form a high octane fuel blending stock, the said normal parafiins being exposed to gamma radiation being gasoline boiling range parafiins from C paraflins to those boiling up to 400 F.

10. A process of claim 3 wherein said paraffin is nhexane.

11. A process of claim 3 wherein said paraffin is npentane.

References Cited in the file of this patent UNITED STATES PATENTS Cier Apr. 28, 1953 OTHER REFERENCES 11, No. 10 (October 

1. A PROCESS OF PRODUCING NAPHTHENES WHICH COMPRISES EXPOSING A PARRAFIN TO A TOTAL DOSAGE OF GAMMA RADIATION OF 1X10**7 TO 1X10**10 REP. UNITS IN THE ABSENCE OF METALLIC VAPORS, AND THEREBY FORMING NAPHTHENES, WHEREIN THE SAID PARAFFIN IS A GASOLINE BOILING RANGE PARAFFIN FROM C5 PARAFFINS TO THOSE BOILING UP TO 400* F. 